A. Field of the Invention
The present invention relates to an inkribbon cartridge for a printer, or more precisely, to the inkribbon cartridge which compulsorily keeps a definite form by a cooperation with its box member and a lid member.
B. Description of the Prior Art
In a ribbon feed mechanism of a printer, an endless inkribbon is stored in an inkribbon cartridge randomly or orderly to be fed successively for printing by a feeding mechanism of the printer. The inkribbon cartridge is mainly composed of a box member and a lid member. A storing portion whose depth is substantially equal to the width of the inkribbon is provided in the box member which has an exit and an inlet for the inkribbon. A plane lid member engages with the box member to complete the inkribbon cartridge.
When the inkribbon is exhausted, the inkribbon cartridge should be exchanged for the next one. Accordingly, it is desirable that the inkribbon cartridge is inexpensive and can be easily mounted on the feeding mechanism and the like.
For this reason, the inkribbon cartridge is in general made of molded plastic resin. But, the inkribbon cartridge, being substantially as long as the printing width, is easily distorted in molding process or by external force. For example, the wall of the box member tends to be bent toward the bottom of the box member or the shape of the inkribbon cartridge is easily deformed. Following that, it becomes difficult to couple the box member with the lid member and, in extreme cases, the shape of the inkribbon cartridge differs with that of predetermined one.
In order to improve the fitness to the feeding mechanism and the like, the shape of the inkribbon cartridge should be arranged according to design. But, there are conflicting problems that, when the extreme accuracy of the molded plastic is required, a special plastic resin and a die for molding is needed. In addition, the cost for production raises by increasing the thickness of the wall or by inferior goods. Moreover, it is not sufficient merely to increase the thickness of the wall or the provision of reinforcement.
In the prior arts, a plurality of projections are provided on the wall of the box member and the projections are inserted into a plurality of holes of the lid member in order to couple them together.
In the above-described construction, however, the contact position of the molded plastic members disagree with each other. So, it is difficult to insert all the projections into holes. The wall of the box member is distorted thereupon and the close fit to the feeding mechanism can not be realized on account of unexpected shape.